Triple Eccentric Butterfly Valve is widely used in petroleum, chemical industry, metallurgy and other fields because of its good sealing and high temperature resistance, to realize the on-off of pipeline system and flow control.

The sealing surface of three eccentric metal hard seal butterfly valve is oblique cone, and the contact between the body seal ring and the sealing ring of the butterfly plate assembly is surface contact. Its working principle is to drive the butterfly plate assembly directly by the torsion of the driving device, so that the butterfly plate assembly seal ring and the body seal ring are fully contacted to produce elastic deformation and seal. Tri-eccentric metal hard-sealed butterfly valve, as a high-performance valve, has the advantages of good corrosion resistance, reliable sealing and small opening moment. Three eccentric hard seal electric butterfly valve DN1200, in which the body sealing ring material is 1Cr18Ni9Ti, the butterfly plate assembly sealing ring material is composite stainless steel plate and asbestos plate sandwich assembly, the processing quality of the body sealing ring and butterfly plate assembly sealing ring directly determines the sealing performance of butterfly valve.

1. Processing Technology

According to the analysis of the structural characteristics of the three-eccentric metal hard-sealed butterfly valve, the sealing ring of the butterfly plate assembly is a combination of stainless steel plate and asbestos plate, and the sealing ring of the valve body is a hard alloy with high hardness. It is difficult to control the feed rate, and it is not easy to be processed and formed at one time, and the roughness of the machined surface is very high. In order to ensure the processing requirements, the process is roughing of valve body or butterfly plate assemblies - carbide overlaying of valve body seal ring - heat preservation for 12h - heat treatment to eliminate thermal stress - sealing surface of rough turning of upper tooling - sealing surface of finishing turning of upper tooling - grinding face of upper grinding head - boring shaft hole - strength test - sealing test of valve body and butterfly plate assemblies.

2. Processing tooling
The sealing ring of butterfly plate assembly and the sealing surface of valve body sealing ring (processing surface) are inclined conical surfaces. The angle between the cone center line and the space vertical line of the valve body seal ring is 8 degrees, and the angle between the cone center line and the space vertical line of the butterfly plate assembly seal ring is 8 degrees. Therefore, the processing tooling for the valve body seal ring (fig. 3) and the processing tooling for the butterfly plate assembly seal ring (fig. 4) are designed.
3 Valve Body Seal Ring Processing
The valve body is sealed as a sealing ring and welded in the valve body (Fig. 5). On 2.5m vertical car, the assembled welded valve body is clamped on the processing tooling of the sealing ring of the valve body, and the tool rod of the vertical lathe is rotated by 8 degrees. According to the design requirements of the drawings, the tool is aligned along the direction of the conical busbar, and the size of the lathe is up to the dimension before the welded stainless steel. Then surfacing stainless steel, Zui will be welded stainless steel valve body on the vertical car again, according to the above method car body seal ring to the size required in the drawings. After Zui, the grinding head is installed on the tool holder of the vertical lathe, and the sealing ring of the valve body is grinded to meet the roughness requirement of the drawing design.
Processing of Seal Ring for 4 Butterfly Plate Components
The sealing part of butterfly plate assembly is a sealing ring. The sealing ring is oblique cone structure. The top angle of the cone is 16 degrees and the thickness is 13.5mm. It is composed of five asbestos plates and four stainless steel plates (Fig. 6). Seal ring must be assembled with butterfly plate and pressing ring, so as to prevent warping deformation of stainless steel plate and asbestos plate in seal ring sandwich. According to its structural characteristics, the following processing methods are adopted for the sealing rings of butterfly board assemblies: (1) Firstly, on a 2.5 m vertical car, each stop on the butterfly board and ring is processed to the required dimensions of the drawings respectively, and the outer circle is not processed; (2) Drilling and tapping the ring according to the drawings; (3) Assembling the ring, ring and plate according to the drawings, fastening the bolts used for assembling butterfly board assemblies to the drawings to the valves. The butterfly plate assemblies are then clamped on the body tools. Vertical turning tool rod rotates 8 degree turning pressure ring, sealing ring and butterfly plate to grinding dimension; (5) replacing sealing ring with the same thickness steel plate, turning pressure ring and butterfly plate conical surface to drawing dimension; (5) fixture is fixed, pressing ring, sealing ring and butterfly plate are reassembled as required, and then grinding head is installed on the vertical turning tool holder to grind the sealing ring to meet the roughness requirement of drawing design.
Machining of 5 Valve Stem Axle Hole
Put the butterfly plate assembly into the valve body, adjust the relative position between the butterfly plate assembly and the valve body, pour into the saponification liquid, no leakage within 5 minutes, press the butterfly plate assembly tightly, and bore the axle hole of the valve body and the butterfly plate.
In this paper, the processing technology, tooling, body seal ring, DISC-PLATE combination seal ring and stem shaft hole of Triple Eccentric Butterfly Valve are introduced. It is efficient and convenient to process valve seal ring and DISC-PLATE combination seal ring, and has good practical value.